King Saud University
College of Applied Medical Science
Department of Optometry
Contact Lenses Cases
Case 1
This patient is collecting a new RGP contact lens. He complains that his vision is blurry with the new lens. An over refraction requires –0.75 DS to bring the visual acuity back to 6/5. What is
the best course of action?
a) Do nothing, the lens will settle in a few hours
b) Order a new lens incorporating the over refraction
c) Order a new lens with a flatter BOZR
d) Order a larger lens
The answer is C
. The picture shows a steep fitting RGP lens. The over refraction of –0.75 suggests that a positive tear lens has formed behind the lens and is the cause of the blurred vision. The answer is to order a flatter lens.
Case 2
This patient has just been fitted with a hydrogel lens for the first time. The picture shows the appearance of the cornea after the lens has been in her eye for a few minutes. The cornea was normal before fitting. What is the best way to manage this patient?
a) Refer immediately to an ophthalmologist
b) Remove the lens and refit with an RGP
c) Advise the patient she is unsuitable for contact lens wear
d) Order this lens anyway
The answer is D
. The slide shows endothelial blebs. These area localised temporary swelling of endothelial cells and are a natural response to soft contact lens wear. The bleb response varies from person to person, it peaks about 20 minutes after insertion and disappears on lens removal. It is less common with high Dk or RGP lenses. Bleb response has little or no clinical significance so this lens can be ordered anyway. To minimise the bleb response an RGP lens could be used instead. Answer B was also marked as correct.
Case 3
This patient is an asymptomatic long term hydrogel lens wearer. The prescription is approximately minus six and he strongly dislikes spectacles. He admits that he occasionally sleeps in his lenses. How would you manage this patient?
a) Cease lens wear all together
b) Cease lens wear for a few weeks then refit with a daily wear silicone hydrogel lens and council the patient about overnight wear
c) Refit straight away with a daily wear silicone hydrogel lens and council the patient about overnight wear
d) Refit straight away with a continuous wear silicone hydrogel lens
The answer is C
. This patient has significant neovascularisation of the cornea, a sign of long term hypoxia. They should be refitted with a high Dk lens such as an RGP or silicone hydrogel. Some practitioners would advocate a temporary cessation of lens wear but this is not normally necessary. Answers B and C were both marked as correct.